The study, published last week in the journal Molecular Ecology, found that the hatchery salmon from the Johnson Creek Artificial Propagation Enhancement program had the same reproductive success when spawning with wild salmon as wild salmon that spawned together.

The findings run counter to some other research and genetic experiments, which have indicated that hatchery-raised fish are less successful than wild salmon. Some biologists and salmon advocates fear that mixing hatchery salmon with wild salmon will ultimately weaken the wild salmon population as a whole.

"Our results question the generalization that all hatchery fish negatively impact the fitness of wild populations," said Maureen Hess, geneticist with the Columbia River Inter-Tribal Fish Commission and lead author on the study.

The researchers compared DNA from all adult salmon that returned to the hatchery over a 13-year span, tracking parents and their offspring. The study found fish taken into the hatchery to spawn produced an average of nearly five times the number of returning adults compared to fish that were left in the wild to spawn.

Hatchery fish that spawned naturally with a wild fish had about the same reproductive success as two wild fish, suggesting that chinook salmon reared for a single generation in the specially-designed hatchery did not reduce the fitness of wild fish.

The Nez Perce Tribe began the Johnson Creek project in 1998 in an effort to boost the low number of salmon that were returning to Idaho rivers to spawn. In 1995, the number of salmon that were counted after returning to Johnson Creek had dropped to five. Today, the number of salmon returning to the creek consistently counted at more than 350 adults, and the numbers have reached more than 1,000 several times.